The central theme of this project is the development and application of photoelectron imaging as a new source of information in the biological sciences. Photoelectron imaging is the electron optical analog of fluorescence microscopy. Fluorescence involves emission of photons against a darker background whereas photoelectron imaging involves emission of electrons. All substances will emit electrons when subjected to UV light of sufficiently short wavelength. Advantages of photoelectron imaging include a new source of contrast (photoelectron quantum yields), very high sensitivity to fine surface detail, low specimen damage compared to microscopes utilizing electron beams, and single protein resolution. As a result of this NCI supported project, the theory of photoelectron imaging has been completed and a high resolution photoelectron microscope constructed for biological applications. This unique facility will be used and improved for two research projects, each with several sub-goals. The first project is DNA imaging. The sub-goals are: Ia) determining the feasibility of obtaining a new type of physical map of DNA ("photoelectron fingerprints") based on differences in photoelectron quantum yields of nucleic acid bases, Ib) extending this idea by examining the photoelectron imaging of dyes intercalated in DNA will the aim of achieving an enhanced brightness modulation along the DNA that could be used for rapid identification of specific regions of DNA of interest in cancer and other medical research (e.g. chromosomal rearrangements, inversions, and specific constructs), and Ic) imaging of small molecule (e.g. carcinogen-DNA interactions using a newly-developed enhancement procedure. The second project involves imaging of cultured mammalian cells (rat embryo fibroblasts, NIH 3T3 and Swiss 3T3 cells), specifically events in the phosphatidylinositol (PI) signal transduction pathway. Sub-goals include: IIa) identifying the location and distribution of protein kinase C and other proteins in the PI pathway, and IIb) examining the mechanism by which the actin cytoskeleton is disrupted by phorbol ester tumor promoters and, independently, by kinase inhibitors H-7, H-9, and staurosporine, molecules thought to bind to enzymes of this signal transduction pathway.